<template>
  <div>
    <h1>当前求和为：{{ sum }}</h1>
    <!-- 加上:都当成js表达式进行运算 -->
    <select v-model.number="n">
     <!--  <option :value="1">1</option>
      <option :value="2">2</option>
      <option :value="3">3</option> -->
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
    </select>
    <button @click="increment">+</button>
    <button @click="decrement">-</button>
    <button @click="incrementOdd">当前求和为奇数再加</button>
    <button @click="incrementWait">等一等再加</button>
  </div>
</template>

<script>
export default {
  name: 'Count',
  data() {
    return {
      n:1,//用户选择的数字
      sum: 0,//当前的和
    }
  },
  methods:{
    increment(){
      this.sum+=this.n
    },
    decrement(){
      this.sum-=this.n
    },
    incrementOdd(){
      if(this.sum%2){
        this.sum+=this.n
      }
    },
    incrementWait(){
      setTimeout(()=>{
        this.sum+=this.n
      },3000)
    },
  }
};
</script>
